text: /*
   * atari_scsi.c -- Device dependent functions for the Atari generic SCSI port
   *
   * Copyright 1994 Roman Hodek <Roman.Hodek@informatik.uni-erlangen.de>
   *
   *   Loosely based on the work of Robert De Vries' team and added:
   *    - working real DMA
   *    - Falcon support (untested yet!)   ++bjoern fixed and now it works
   *    - lots of extensions and bug fixes.
   *
   * This file is subject to the terms and conditions of the GNU General Public
   * License.  See the file COPYING in the main directory of this archive
   * for more details.
   *
   */
  
  /*
   * Notes for Falcon SCSI DMA
   *
   * The 5380 device is one of several that all share the DMA chip. Hence
   * "locking" and "unlocking" access to this chip is required.
   *
   * Two possible schemes for ST DMA acquisition by atari_scsi are:
   * 1) The lock is taken for each command separately (i.e. can_queue == 1).
   * 2) The lock is taken when the first command arrives and released
   * when the last command is finished (i.e. can_queue > 1).
   *
   * The first alternative limits SCSI bus utilization, since interleaving
   * commands is not possible. The second gives better performance but is
   * unfair to other drivers needing to use the ST DMA chip. In order to
   * allow the IDE and floppy drivers equal access to the ST DMA chip
   * the default is can_queue == 1.
   */
  
  #include <linux/module.h>
  #include <linux/types.h>
  #include <linux/blkdev.h>
  #include <linux/interrupt.h>
  #include <linux/init.h>
  #include <linux/nvram.h>
  #include <linux/bitops.h>
  #include <linux/wait.h>
  #include <linux/platform_device.h>
  
  #include <asm/setup.h>
  #include <asm/atarihw.h>
  #include <asm/atariints.h>
  #include <asm/atari_stdma.h>
  #include <asm/atari_stram.h>
  #include <asm/io.h>
  
  #include <scsi/scsi_host.h>
  
  #define DMA_MIN_SIZE                    32
  
  /* Definitions for the core NCR5380 driver. */
  
  #define NCR5380_implementation_fields   /* none */
  
  static u8 (*atari_scsi_reg_read)(unsigned int);
  static void (*atari_scsi_reg_write)(unsigned int, u8);
  
  #define NCR5380_read(reg)               atari_scsi_reg_read(reg)
  #define NCR5380_write(reg, value)       atari_scsi_reg_write(reg, value)
  
  #define NCR5380_queue_command           atari_scsi_queue_command
  #define NCR5380_abort                   atari_scsi_abort
  #define NCR5380_info                    atari_scsi_info
  
  #define NCR5380_dma_xfer_len            atari_scsi_dma_xfer_len
  #define NCR5380_dma_recv_setup          atari_scsi_dma_recv_setup
  #define NCR5380_dma_send_setup          atari_scsi_dma_send_setup
  #define NCR5380_dma_residual            atari_scsi_dma_residual
  
  #define NCR5380_acquire_dma_irq(instance)      falcon_get_lock(instance)
  #define NCR5380_release_dma_irq(instance)      falcon_release_lock()
  
  #include "NCR5380.h"
  
  
  #define	IS_A_TT()	ATARIHW_PRESENT(TT_SCSI)
  
  #define	SCSI_DMA_WRITE_P(elt,val)				\
  	do {							\
  		unsigned long v = val;				\
  		tt_scsi_dma.elt##_lo = v & 0xff;		\
  		v >>= 8;					\
  		tt_scsi_dma.elt##_lmd = v & 0xff;		\
  		v >>= 8;					\
  		tt_scsi_dma.elt##_hmd = v & 0xff;		\
  		v >>= 8;					\
  		tt_scsi_dma.elt##_hi = v & 0xff;		\
  	} while(0)
  
  #define	SCSI_DMA_READ_P(elt)					\
  	(((((((unsigned long)tt_scsi_dma.elt##_hi << 8) |	\
  	     (unsigned long)tt_scsi_dma.elt##_hmd) << 8) |	\
  	   (unsigned long)tt_scsi_dma.elt##_lmd) << 8) |	\
  	 (unsigned long)tt_scsi_dma.elt##_lo)
  
  
  static inline void SCSI_DMA_SETADR(unsigned long adr)
  {
  	st_dma.dma_lo = (unsigned char)adr;
  	MFPDELAY();
  	adr >>= 8;
  	st_dma.dma_md = (unsigned char)adr;
  	MFPDELAY();
  	adr >>= 8;
  	st_dma.dma_hi = (unsigned char)adr;
  	MFPDELAY();
  }
  
  static inline unsigned long SCSI_DMA_GETADR(void)
  {
  	unsigned long adr;
  	adr = st_dma.dma_lo;
  	MFPDELAY();
  	adr |= (st_dma.dma_md & 0xff) << 8;
  	MFPDELAY();
  	adr |= (st_dma.dma_hi & 0xff) << 16;
  	MFPDELAY();
  	return adr;
  }
  
  static void atari_scsi_fetch_restbytes(void);
  
  static unsigned long	atari_dma_residual, atari_dma_startaddr;
  static short		atari_dma_active;
  /* pointer to the dribble buffer */
  static char		*atari_dma_buffer;
  /* precalculated physical address of the dribble buffer */
  static unsigned long	atari_dma_phys_buffer;
  /* != 0 tells the Falcon int handler to copy data from the dribble buffer */
  static char		*atari_dma_orig_addr;
  /* size of the dribble buffer; 4k seems enough, since the Falcon cannot use
   * scatter-gather anyway, so most transfers are 1024 byte only. In the rare
   * cases where requests to physical contiguous buffers have been merged, this
   * request is <= 4k (one page). So I don't think we have to split transfers
   * just due to this buffer size...
   */
  #define	STRAM_BUFFER_SIZE	(4096)
  /* mask for address bits that can't be used with the ST-DMA */
  static unsigned long	atari_dma_stram_mask;
  #define STRAM_ADDR(a)	(((a) & atari_dma_stram_mask) == 0)
  
  static int setup_can_queue = -1;
  module_param(setup_can_queue, int, 0);
  static int setup_cmd_per_lun = -1;
  module_param(setup_cmd_per_lun, int, 0);
  static int setup_sg_tablesize = -1;
  module_param(setup_sg_tablesize, int, 0);
  static int setup_hostid = -1;
  module_param(setup_hostid, int, 0);
  static int setup_toshiba_delay = -1;
  module_param(setup_toshiba_delay, int, 0);
  
  
  static int scsi_dma_is_ignored_buserr(unsigned char dma_stat)
  {
  	int i;
  	unsigned long addr = SCSI_DMA_READ_P(dma_addr), end_addr;
  
  	if (dma_stat & 0x01) {
  
  		/* A bus error happens when DMA-ing from the last page of a
  		 * physical memory chunk (DMA prefetch!), but that doesn't hurt.
  		 * Check for this case:
  		 */
  
  		for (i = 0; i < m68k_num_memory; ++i) {
  			end_addr = m68k_memory[i].addr + m68k_memory[i].size;
  			if (end_addr <= addr && addr <= end_addr + 4)
  				return 1;
  		}
  	}
  	return 0;
  }
  
  
  static irqreturn_t scsi_tt_intr(int irq, void *dev)
  {
  	struct Scsi_Host *instance = dev;
  	struct NCR5380_hostdata *hostdata = shost_priv(instance);
  	int dma_stat;
  
  	dma_stat = tt_scsi_dma.dma_ctrl;
  
  	dsprintk(NDEBUG_INTR, instance, "NCR5380 interrupt, DMA status = %02x\n",
  	         dma_stat & 0xff);
  
  	/* Look if it was the DMA that has interrupted: First possibility
  	 * is that a bus error occurred...
  	 */
  	if (dma_stat & 0x80) {
  		if (!scsi_dma_is_ignored_buserr(dma_stat)) {
  			printk(KERN_ERR "SCSI DMA caused bus error near 0x%08lx\n",
  			       SCSI_DMA_READ_P(dma_addr));
  			printk(KERN_CRIT "SCSI DMA bus error -- bad DMA programming!");
  		}
  	}
  
  	/* If the DMA is active but not finished, we have the case
  	 * that some other 5380 interrupt occurred within the DMA transfer.
  	 * This means we have residual bytes, if the desired end address
  	 * is not yet reached. Maybe we have to fetch some bytes from the
  	 * rest data register, too. The residual must be calculated from
  	 * the address pointer, not the counter register, because only the
  	 * addr reg counts bytes not yet written and pending in the rest
  	 * data reg!
  	 */
  	if ((dma_stat & 0x02) && !(dma_stat & 0x40)) {
  		atari_dma_residual = hostdata->dma_len -
  			(SCSI_DMA_READ_P(dma_addr) - atari_dma_startaddr);
  
  		dprintk(NDEBUG_DMA, "SCSI DMA: There are %ld residual bytes.\n",
  			   atari_dma_residual);
  
  		if ((signed int)atari_dma_residual < 0)
  			atari_dma_residual = 0;
  		if ((dma_stat & 1) == 0) {
  			/*
  			 * After read operations, we maybe have to
  			 * transport some rest bytes
  			 */
  			atari_scsi_fetch_restbytes();
  		} else {
  			/*
  			 * There seems to be a nasty bug in some SCSI-DMA/NCR
  			 * combinations: If a target disconnects while a write
  			 * operation is going on, the address register of the
  			 * DMA may be a few bytes farer than it actually read.
  			 * This is probably due to DMA prefetching and a delay
  			 * between DMA and NCR.  Experiments showed that the
  			 * dma_addr is 9 bytes to high, but this could vary.
  			 * The problem is, that the residual is thus calculated
  			 * wrong and the next transfer will start behind where
  			 * it should.  So we round up the residual to the next
  			 * multiple of a sector size, if it isn't already a
  			 * multiple and the originally expected transfer size
  			 * was.  The latter condition is there to ensure that
  			 * the correction is taken only for "real" data
  			 * transfers and not for, e.g., the parameters of some
  			 * other command.  These shouldn't disconnect anyway.
  			 */
  			if (atari_dma_residual & 0x1ff) {
  				dprintk(NDEBUG_DMA, "SCSI DMA: DMA bug corrected, "
  					   "difference %ld bytes\n",
  					   512 - (atari_dma_residual & 0x1ff));
  				atari_dma_residual = (atari_dma_residual + 511) & ~0x1ff;
  			}
  		}
  		tt_scsi_dma.dma_ctrl = 0;
  	}
  
  	/* If the DMA is finished, fetch the rest bytes and turn it off */
  	if (dma_stat & 0x40) {
  		atari_dma_residual = 0;
  		if ((dma_stat & 1) == 0)
  			atari_scsi_fetch_restbytes();
  		tt_scsi_dma.dma_ctrl = 0;
  	}
  
  	NCR5380_intr(irq, dev);
  
  	return IRQ_HANDLED;
  }
  
  
  static irqreturn_t scsi_falcon_intr(int irq, void *dev)
  {
  	struct Scsi_Host *instance = dev;
  	struct NCR5380_hostdata *hostdata = shost_priv(instance);
  	int dma_stat;
  
  	/* Turn off DMA and select sector counter register before
  	 * accessing the status register (Atari recommendation!)
  	 */
  	st_dma.dma_mode_status = 0x90;
  	dma_stat = st_dma.dma_mode_status;
  
  	/* Bit 0 indicates some error in the DMA process... don't know
  	 * what happened exactly (no further docu).
  	 */
  	if (!(dma_stat & 0x01)) {
  		/* DMA error */
  		printk(KERN_CRIT "SCSI DMA error near 0x%08lx!\n", SCSI_DMA_GETADR());
  	}
  
  	/* If the DMA was active, but now bit 1 is not clear, it is some
  	 * other 5380 interrupt that finishes the DMA transfer. We have to
  	 * calculate the number of residual bytes and give a warning if
  	 * bytes are stuck in the ST-DMA fifo (there's no way to reach them!)
  	 */
  	if (atari_dma_active && (dma_stat & 0x02)) {
  		unsigned long transferred;
  
  		transferred = SCSI_DMA_GETADR() - atari_dma_startaddr;
  		/* The ST-DMA address is incremented in 2-byte steps, but the
  		 * data are written only in 16-byte chunks. If the number of
  		 * transferred bytes is not divisible by 16, the remainder is
  		 * lost somewhere in outer space.
  		 */
  		if (transferred & 15)
  			printk(KERN_ERR "SCSI DMA error: %ld bytes lost in "
  			       "ST-DMA fifo\n", transferred & 15);
  
  		atari_dma_residual = hostdata->dma_len - transferred;
  		dprintk(NDEBUG_DMA, "SCSI DMA: There are %ld residual bytes.\n",
  			   atari_dma_residual);
  	} else
  		atari_dma_residual = 0;
  	atari_dma_active = 0;
  
  	if (atari_dma_orig_addr) {
  		/* If the dribble buffer was used on a read operation, copy the DMA-ed
  		 * data to the original destination address.
  		 */
  		memcpy(atari_dma_orig_addr, phys_to_virt(atari_dma_startaddr),
  		       hostdata->dma_len - atari_dma_residual);
  		atari_dma_orig_addr = NULL;
  	}
  
  	NCR5380_intr(irq, dev);
  
  	return IRQ_HANDLED;
  }
  
  
  static void atari_scsi_fetch_restbytes(void)
  {
  	int nr;
  	char *src, *dst;
  	unsigned long phys_dst;
  
  	/* fetch rest bytes in the DMA register */
  	phys_dst = SCSI_DMA_READ_P(dma_addr);
  	nr = phys_dst & 3;
  	if (nr) {
  		/* there are 'nr' bytes left for the last long address
  		   before the DMA pointer */
  		phys_dst ^= nr;
  		dprintk(NDEBUG_DMA, "SCSI DMA: there are %d rest bytes for phys addr 0x%08lx",
  			   nr, phys_dst);
  		/* The content of the DMA pointer is a physical address!  */
  		dst = phys_to_virt(phys_dst);
  		dprintk(NDEBUG_DMA, " = virt addr %p\n", dst);
  		for (src = (char *)&tt_scsi_dma.dma_restdata; nr != 0; --nr)
  			*dst++ = *src++;
  	}
  }
  
  
  /* This function releases the lock on the DMA chip if there is no
   * connected command and the disconnected queue is empty.
   */
  
  static void falcon_release_lock(void)
  {
  	if (IS_A_TT())
  		return;
  
  	if (stdma_is_locked_by(scsi_falcon_intr))
  		stdma_release();
  }
  
  /* This function manages the locking of the ST-DMA.
   * If the DMA isn't locked already for SCSI, it tries to lock it by
   * calling stdma_lock(). But if the DMA is locked by the SCSI code and
   * there are other drivers waiting for the chip, we do not issue the
   * command immediately but tell the SCSI mid-layer to defer.
   */
  
  static int falcon_get_lock(struct Scsi_Host *instance)
  {
  	if (IS_A_TT())
  		return 1;
  
  	if (stdma_is_locked_by(scsi_falcon_intr) &&
  	    instance->hostt->can_queue > 1)
  		return 1;
  
  	if (in_interrupt())
  		return stdma_try_lock(scsi_falcon_intr, instance);
  
  	stdma_lock(scsi_falcon_intr, instance);
  	return 1;
  }
  
  #ifndef MODULE
  static int __init atari_scsi_setup(char *str)
  {
  	/* Format of atascsi parameter is:
  	 *   atascsi=<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
  	 * Defaults depend on TT or Falcon, determined at run time.
  	 * Negative values mean don't change.
  	 */
  	int ints[8];
  
  	get_options(str, ARRAY_SIZE(ints), ints);
  
  	if (ints[0] < 1) {
  		printk("atari_scsi_setup: no arguments!\n");
  		return 0;
  	}
  	if (ints[0] >= 1)
  		setup_can_queue = ints[1];
  	if (ints[0] >= 2)
  		setup_cmd_per_lun = ints[2];
  	if (ints[0] >= 3)
  		setup_sg_tablesize = ints[3];
  	if (ints[0] >= 4)
  		setup_hostid = ints[4];
  	/* ints[5] (use_tagged_queuing) is ignored */
  	/* ints[6] (use_pdma) is ignored */
  	if (ints[0] >= 7)
  		setup_toshiba_delay = ints[7];
  
  	return 1;
  }
  
  __setup("atascsi=", atari_scsi_setup);
  #endif /* !MODULE */
  
  static unsigned long atari_scsi_dma_setup(struct NCR5380_hostdata *hostdata,
  					  void *data, unsigned long count,
  					  int dir)
  {
  	unsigned long addr = virt_to_phys(data);
  
  	dprintk(NDEBUG_DMA, "scsi%d: setting up dma, data = %p, phys = %lx, count = %ld, dir = %d\n",
  	        hostdata->host->host_no, data, addr, count, dir);
  
  	if (!IS_A_TT() && !STRAM_ADDR(addr)) {
  		/* If we have a non-DMAable address on a Falcon, use the dribble
  		 * buffer; 'orig_addr' != 0 in the read case tells the interrupt
  		 * handler to copy data from the dribble buffer to the originally
  		 * wanted address.
  		 */
  		if (dir)
  			memcpy(atari_dma_buffer, data, count);
  		else
  			atari_dma_orig_addr = data;
  		addr = atari_dma_phys_buffer;
  	}
  
  	atari_dma_startaddr = addr;	/* Needed for calculating residual later. */
  
  	/* Cache cleanup stuff: On writes, push any dirty cache out before sending
  	 * it to the peripheral. (Must be done before DMA setup, since at least
  	 * the ST-DMA begins to fill internal buffers right after setup. For
  	 * reads, invalidate any cache, may be altered after DMA without CPU
  	 * knowledge.
  	 *
  	 * ++roman: For the Medusa, there's no need at all for that cache stuff,
  	 * because the hardware does bus snooping (fine!).
  	 */
  	dma_cache_maintenance(addr, count, dir);
  
  	if (IS_A_TT()) {
  		tt_scsi_dma.dma_ctrl = dir;
  		SCSI_DMA_WRITE_P(dma_addr, addr);
  		SCSI_DMA_WRITE_P(dma_cnt, count);
  		tt_scsi_dma.dma_ctrl = dir | 2;
  	} else { /* ! IS_A_TT */
  
  		/* set address */
  		SCSI_DMA_SETADR(addr);
  
  		/* toggle direction bit to clear FIFO and set DMA direction */
  		dir <<= 8;
  		st_dma.dma_mode_status = 0x90 | dir;
  		st_dma.dma_mode_status = 0x90 | (dir ^ 0x100);
  		st_dma.dma_mode_status = 0x90 | dir;
  		udelay(40);
  		/* On writes, round up the transfer length to the next multiple of 512
  		 * (see also comment at atari_dma_xfer_len()). */
  		st_dma.fdc_acces_seccount = (count + (dir ? 511 : 0)) >> 9;
  		udelay(40);
  		st_dma.dma_mode_status = 0x10 | dir;
  		udelay(40);
  		/* need not restore value of dir, only boolean value is tested */
  		atari_dma_active = 1;
  	}
  
  	return count;
  }
  
  static inline int atari_scsi_dma_recv_setup(struct NCR5380_hostdata *hostdata,
                                              unsigned char *data, int count)
  {
  	return atari_scsi_dma_setup(hostdata, data, count, 0);
  }
  
  static inline int atari_scsi_dma_send_setup(struct NCR5380_hostdata *hostdata,
                                              unsigned char *data, int count)
  {
  	return atari_scsi_dma_setup(hostdata, data, count, 1);
  }
  
  static int atari_scsi_dma_residual(struct NCR5380_hostdata *hostdata)
  {
  	return atari_dma_residual;
  }
  
  
  #define	CMD_SURELY_BLOCK_MODE	0
  #define	CMD_SURELY_BYTE_MODE	1
  #define	CMD_MODE_UNKNOWN		2
  
  static int falcon_classify_cmd(struct scsi_cmnd *cmd)
  {
  	unsigned char opcode = cmd->cmnd[0];
  
  	if (opcode == READ_DEFECT_DATA || opcode == READ_LONG ||
  	    opcode == READ_BUFFER)
  		return CMD_SURELY_BYTE_MODE;
  	else if (opcode == READ_6 || opcode == READ_10 ||
  		 opcode == 0xa8 /* READ_12 */ || opcode == READ_REVERSE ||
  		 opcode == RECOVER_BUFFERED_DATA) {
  		/* In case of a sequential-access target (tape), special care is
  		 * needed here: The transfer is block-mode only if the 'fixed' bit is
  		 * set! */
  		if (cmd->device->type == TYPE_TAPE && !(cmd->cmnd[1] & 1))
  			return CMD_SURELY_BYTE_MODE;
  		else
  			return CMD_SURELY_BLOCK_MODE;
  	} else
  		return CMD_MODE_UNKNOWN;
  }
  
  
  /* This function calculates the number of bytes that can be transferred via
   * DMA. On the TT, this is arbitrary, but on the Falcon we have to use the
   * ST-DMA chip. There are only multiples of 512 bytes possible and max.
   * 255*512 bytes :-( This means also, that defining READ_OVERRUNS is not
   * possible on the Falcon, since that would require to program the DMA for
   * n*512 - atari_read_overrun bytes. But it seems that the Falcon doesn't have
   * the overrun problem, so this question is academic :-)
   */
  
  static int atari_scsi_dma_xfer_len(struct NCR5380_hostdata *hostdata,
                                     struct scsi_cmnd *cmd)
  {
  	int wanted_len = cmd->SCp.this_residual;
  	int possible_len, limit;
  
  	if (wanted_len < DMA_MIN_SIZE)
  		return 0;
  
  	if (IS_A_TT())
  		/* TT SCSI DMA can transfer arbitrary #bytes */
  		return wanted_len;
  
  	/* ST DMA chip is stupid -- only multiples of 512 bytes! (and max.
  	 * 255*512 bytes, but this should be enough)
  	 *
  	 * ++roman: Aaargl! Another Falcon-SCSI problem... There are some commands
  	 * that return a number of bytes which cannot be known beforehand. In this
  	 * case, the given transfer length is an "allocation length". Now it
  	 * can happen that this allocation length is a multiple of 512 bytes and
  	 * the DMA is used. But if not n*512 bytes really arrive, some input data
  	 * will be lost in the ST-DMA's FIFO :-( Thus, we have to distinguish
  	 * between commands that do block transfers and those that do byte
  	 * transfers. But this isn't easy... there are lots of vendor specific
  	 * commands, and the user can issue any command via the
  	 * SCSI_IOCTL_SEND_COMMAND.
  	 *
  	 * The solution: We classify SCSI commands in 1) surely block-mode cmd.s,
  	 * 2) surely byte-mode cmd.s and 3) cmd.s with unknown mode. In case 1)
  	 * and 3), the thing to do is obvious: allow any number of blocks via DMA
  	 * or none. In case 2), we apply some heuristic: Byte mode is assumed if
  	 * the transfer (allocation) length is < 1024, hoping that no cmd. not
  	 * explicitly known as byte mode have such big allocation lengths...
  	 * BTW, all the discussion above applies only to reads. DMA writes are
  	 * unproblematic anyways, since the targets aborts the transfer after
  	 * receiving a sufficient number of bytes.
  	 *
  	 * Another point: If the transfer is from/to an non-ST-RAM address, we
  	 * use the dribble buffer and thus can do only STRAM_BUFFER_SIZE bytes.
  	 */
  
  	if (cmd->sc_data_direction == DMA_TO_DEVICE) {
  		/* Write operation can always use the DMA, but the transfer size must
  		 * be rounded up to the next multiple of 512 (atari_dma_setup() does
  		 * this).
  		 */
  		possible_len = wanted_len;
  	} else {
  		/* Read operations: if the wanted transfer length is not a multiple of
  		 * 512, we cannot use DMA, since the ST-DMA cannot split transfers
  		 * (no interrupt on DMA finished!)
  		 */
  		if (wanted_len & 0x1ff)
  			possible_len = 0;
  		else {
  			/* Now classify the command (see above) and decide whether it is
  			 * allowed to do DMA at all */
  			switch (falcon_classify_cmd(cmd)) {
  			case CMD_SURELY_BLOCK_MODE:
  				possible_len = wanted_len;
  				break;
  			case CMD_SURELY_BYTE_MODE:
  				possible_len = 0; /* DMA prohibited */
  				break;
  			case CMD_MODE_UNKNOWN:
  			default:
  				/* For unknown commands assume block transfers if the transfer
  				 * size/allocation length is >= 1024 */
  				possible_len = (wanted_len < 1024) ? 0 : wanted_len;
  				break;
  			}
  		}
  	}
  
  	/* Last step: apply the hard limit on DMA transfers */
  	limit = (atari_dma_buffer && !STRAM_ADDR(virt_to_phys(cmd->SCp.ptr))) ?
  		    STRAM_BUFFER_SIZE : 255*512;
  	if (possible_len > limit)
  		possible_len = limit;
  
  	if (possible_len != wanted_len)
  		dprintk(NDEBUG_DMA, "DMA transfer now %d bytes instead of %d\n",
  		        possible_len, wanted_len);
  
  	return possible_len;
  }
  
  
  /* NCR5380 register access functions
   *
   * There are separate functions for TT and Falcon, because the access
   * methods are quite different. The calling macros NCR5380_read and
   * NCR5380_write call these functions via function pointers.
   */
  
  static u8 atari_scsi_tt_reg_read(unsigned int reg)
  {
  	return tt_scsi_regp[reg * 2];
  }
  
  static void atari_scsi_tt_reg_write(unsigned int reg, u8 value)
  {
  	tt_scsi_regp[reg * 2] = value;
  }
  
  static u8 atari_scsi_falcon_reg_read(unsigned int reg)
  {
  	unsigned long flags;
  	u8 result;
  
  	reg += 0x88;
  	local_irq_save(flags);
  	dma_wd.dma_mode_status = (u_short)reg;
  	result = (u8)dma_wd.fdc_acces_seccount;
  	local_irq_restore(flags);
  	return result;
  }
  
  static void atari_scsi_falcon_reg_write(unsigned int reg, u8 value)
  {
  	unsigned long flags;
  
  	reg += 0x88;
  	local_irq_save(flags);
  	dma_wd.dma_mode_status = (u_short)reg;
  	dma_wd.fdc_acces_seccount = (u_short)value;
  	local_irq_restore(flags);
  }
  
  
  #include "NCR5380.c"
  
  static int atari_scsi_host_reset(struct scsi_cmnd *cmd)
  {
  	int rv;
  	unsigned long flags;
  
  	local_irq_save(flags);
  
  	/* Abort a maybe active DMA transfer */
  	if (IS_A_TT()) {
  		tt_scsi_dma.dma_ctrl = 0;
  	} else {
  		if (stdma_is_locked_by(scsi_falcon_intr))
  			st_dma.dma_mode_status = 0x90;
  		atari_dma_active = 0;
  		atari_dma_orig_addr = NULL;
  	}
  
  	rv = NCR5380_host_reset(cmd);
  
  	/* The 5380 raises its IRQ line while _RST is active but the ST DMA
  	 * "lock" has been released so this interrupt may end up handled by
  	 * floppy or IDE driver (if one of them holds the lock). The NCR5380
  	 * interrupt flag has been cleared already.
  	 */
  
  	local_irq_restore(flags);
  
  	return rv;
  }
  
  #define DRV_MODULE_NAME         "atari_scsi"
  #define PFX                     DRV_MODULE_NAME ": "
  
  static struct scsi_host_template atari_scsi_template = {
  	.module			= THIS_MODULE,
  	.proc_name		= DRV_MODULE_NAME,
  	.name			= "Atari native SCSI",
  	.info			= atari_scsi_info,
  	.queuecommand		= atari_scsi_queue_command,
  	.eh_abort_handler	= atari_scsi_abort,
  	.eh_host_reset_handler	= atari_scsi_host_reset,
  	.this_id		= 7,
  	.cmd_per_lun		= 2,
  	.dma_boundary		= PAGE_SIZE - 1,
  	.cmd_size		= NCR5380_CMD_SIZE,
  };
  
  static int __init atari_scsi_probe(struct platform_device *pdev)
  {
  	struct Scsi_Host *instance;
  	int error;
  	struct resource *irq;
  	int host_flags = 0;
  
  	irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
  	if (!irq)
  		return -ENODEV;
  
  	if (ATARIHW_PRESENT(TT_SCSI)) {
  		atari_scsi_reg_read  = atari_scsi_tt_reg_read;
  		atari_scsi_reg_write = atari_scsi_tt_reg_write;
  	} else {
  		atari_scsi_reg_read  = atari_scsi_falcon_reg_read;
  		atari_scsi_reg_write = atari_scsi_falcon_reg_write;
  	}
  
  	if (ATARIHW_PRESENT(TT_SCSI)) {
  		atari_scsi_template.can_queue    = 16;
  		atari_scsi_template.sg_tablesize = SG_ALL;
  	} else {
  		atari_scsi_template.can_queue    = 1;
  		atari_scsi_template.sg_tablesize = 1;
  	}
  
  	if (setup_can_queue > 0)
  		atari_scsi_template.can_queue = setup_can_queue;
  
  	if (setup_cmd_per_lun > 0)
  		atari_scsi_template.cmd_per_lun = setup_cmd_per_lun;
  
  	/* Don't increase sg_tablesize on Falcon! */
  	if (ATARIHW_PRESENT(TT_SCSI) && setup_sg_tablesize > 0)
  		atari_scsi_template.sg_tablesize = setup_sg_tablesize;
  
  	if (setup_hostid >= 0) {
  		atari_scsi_template.this_id = setup_hostid & 7;
  	} else if (IS_REACHABLE(CONFIG_NVRAM)) {
  		/* Test if a host id is set in the NVRam */
  		if (ATARIHW_PRESENT(TT_CLK)) {
  			unsigned char b;
  			loff_t offset = 16;
  			ssize_t count = nvram_read(&b, 1, &offset);
  
  			/* Arbitration enabled? (for TOS)
  			 * If yes, use configured host ID
  			 */
  			if ((count == 1) && (b & 0x80))
  				atari_scsi_template.this_id = b & 7;
  		}
  	}
  
  	/* If running on a Falcon and if there's TT-Ram (i.e., more than one
  	 * memory block, since there's always ST-Ram in a Falcon), then
  	 * allocate a STRAM_BUFFER_SIZE byte dribble buffer for transfers
  	 * from/to alternative Ram.
  	 */
  	if (ATARIHW_PRESENT(ST_SCSI) && !ATARIHW_PRESENT(EXTD_DMA) &&
  	    m68k_realnum_memory > 1) {
  		atari_dma_buffer = atari_stram_alloc(STRAM_BUFFER_SIZE, "SCSI");
  		if (!atari_dma_buffer) {
  			pr_err(PFX "can't allocate ST-RAM double buffer\n");
  			return -ENOMEM;
  		}
  		atari_dma_phys_buffer = atari_stram_to_phys(atari_dma_buffer);
  		atari_dma_orig_addr = NULL;
  	}
  
  	instance = scsi_host_alloc(&atari_scsi_template,
  	                           sizeof(struct NCR5380_hostdata));
  	if (!instance) {
  		error = -ENOMEM;
  		goto fail_alloc;
  	}
  
  	instance->irq = irq->start;
  
  	host_flags |= IS_A_TT() ? 0 : FLAG_LATE_DMA_SETUP;
  	host_flags |= setup_toshiba_delay > 0 ? FLAG_TOSHIBA_DELAY : 0;
  
  	error = NCR5380_init(instance, host_flags);
  	if (error)
  		goto fail_init;
  
  	if (IS_A_TT()) {
  		error = request_irq(instance->irq, scsi_tt_intr, 0,
  		                    "NCR5380", instance);
  		if (error) {
  			pr_err(PFX "request irq %d failed, aborting\n",
  			       instance->irq);
  			goto fail_irq;
  		}
  		tt_mfp.active_edge |= 0x80;	/* SCSI int on L->H */
  
  		tt_scsi_dma.dma_ctrl = 0;
  		atari_dma_residual = 0;
  
  		/* While the read overruns (described by Drew Eckhardt in
  		 * NCR5380.c) never happened on TTs, they do in fact on the
  		 * Medusa (This was the cause why SCSI didn't work right for
  		 * so long there.) Since handling the overruns slows down
  		 * a bit, I turned the #ifdef's into a runtime condition.
  		 *
  		 * In principle it should be sufficient to do max. 1 byte with
  		 * PIO, but there is another problem on the Medusa with the DMA
  		 * rest data register. So read_overruns is currently set
  		 * to 4 to avoid having transfers that aren't a multiple of 4.
  		 * If the rest data bug is fixed, this can be lowered to 1.
  		 */
  		if (MACH_IS_MEDUSA) {
  			struct NCR5380_hostdata *hostdata =
  				shost_priv(instance);
  
  			hostdata->read_overruns = 4;
  		}
  	} else {
  		/* Nothing to do for the interrupt: the ST-DMA is initialized
  		 * already.
  		 */
  		atari_dma_residual = 0;
  		atari_dma_active = 0;
  		atari_dma_stram_mask = (ATARIHW_PRESENT(EXTD_DMA) ? 0x00000000
  					: 0xff000000);
  	}
  
  	NCR5380_maybe_reset_bus(instance);
  
  	error = scsi_add_host(instance, NULL);
  	if (error)
  		goto fail_host;
  
  	platform_set_drvdata(pdev, instance);
  
  	scsi_scan_host(instance);
  	return 0;
  
  fail_host:
  	if (IS_A_TT())
  		free_irq(instance->irq, instance);
  fail_irq:
  	NCR5380_exit(instance);
  fail_init:
  	scsi_host_put(instance);
  fail_alloc:
  	if (atari_dma_buffer)
  		atari_stram_free(atari_dma_buffer);
  	return error;
  }
  
  static int __exit atari_scsi_remove(struct platform_device *pdev)
  {
  	struct Scsi_Host *instance = platform_get_drvdata(pdev);
  
  	scsi_remove_host(instance);
  	if (IS_A_TT())
  		free_irq(instance->irq, instance);
  	NCR5380_exit(instance);
  	scsi_host_put(instance);
  	if (atari_dma_buffer)
  		atari_stram_free(atari_dma_buffer);
  	return 0;
  }
  
  static struct platform_driver atari_scsi_driver = {
  	.remove = __exit_p(atari_scsi_remove),
  	.driver = {
  		.name	= DRV_MODULE_NAME,
  	},
  };
  
  module_platform_driver_probe(atari_scsi_driver, atari_scsi_probe);
  
  MODULE_ALIAS("platform:" DRV_MODULE_NAME);
  MODULE_LICENSE("GPL");
  